Project Summary In recent years, it has been become clear that modulating the peripheral nervous system has great potential for treating diseases. To realize this potential, a new neuromodulation modality is needed that is safe, highly specific, and rapidly reversible. We have recently shown that infrared neuromodulation (IRN) when applied to peripheral structures such as the nodose ganglion induces unique patterns of physiological responses that cannot be elicited by electrical current or drugs. The nodose ganglion plays an important role in regulating many critical autonomic functions, and IRN application has unmasked a functional organization for different sub-regions of the ganglion that has not been previously described. These results suggest that IRN has enormous potential for mapping the topology of functional responses in ganglia, decoding ganglionic circuitry, and as a clinical neuroceutical device. IRN stimulates neural activity by inducing a brief spatiotemporal temperature gradient or inhibits activity by increasing the baseline temperature. We propose to advance IRN and imaging technology in the following ways. First, we will to create new devices to efficiently and precisely deliver IR light to nerves and ganglia in animals. New devices include flexible polymer waveguides that can deliver light to multiple locations while conforming and moving freely with the target tissue, a ganglia tracking system that can identify the orientation of the nodose ganglion and precisely control IR illumination patterns on the ganglia for mapping function, and advanced calcium imaging systems that can do volumetric imaging of ganglionic activity and imaging in living animals. Second, we will assess the safety, selectivity, and repeatability of IRN. Third, we will develop a deep understanding of how IRN works by conducting mechanistic studies that include creating sophisticated models of IRN?s effect on electrophysiology and experiments to test our hypotheses. Fourth, because IRN has unmasked a spatial organization to ganglionic function, we will be able to map this organization in detail and provide an unprecedented understanding of ganglionic function. The tools and knowledge gained in this grant will not only help determine the potential of IRN, but be beneficial to a host of future neuromodulation and other applications.